1. Field of the Invention
The invention relates to a guide bush for an adjustable length column for chairs, tables or the like, which, in its inner portion, is provided with a slide bush concentric of a central longitudinal axis for the guidance of a cylindrical housing of an adjusting element, the outside wall of the slide bush being provided with spaced ribs for the reception and support, radial to the axis, in an upright tube of the column, and to an adjustable length column comprising a guide bush of this type.
2. Background Art
A guide bush of the generic type and a column of the generic type are known from U.S. Pat. No. 5,496,115. On the inside circumference of its slide bush, this known guide bush comprises narrow guide ribs for the guidance of the housing of an adjusting element, in particular an adjustable length gas spring. Web-like ribs are formed on the outside circumference of the slide bush, extending precisely radially to the common central longitudinal axis and supporting the slide bush to be rigid and immovable radially to the central longitudinal axis in the upright tube of the column. The web-like ribs combine with the slide bush to be very rigid so that no inadvertent radial motions of the housing of the adjustable length element are possible.
Any direct compensation of tolerances of the inside diameter of the upright tube is not possible in this way.
In as much as the design of the web-like ribs and the support, in this regard rigid radially to the central longitudinal axis, of the slide bush in an upright tube are concerned, comparable solutions are known from U.S. Pat. No. 5,152,646 and U.S. Pat. No. 4,899,969.
U.S. Pat. No. 5,161,786 teaches an upright tube of plastic material which is embodied to replace an upright tube of metal. It comprises rigid web-like ribs on its inner surface which extend over the full length thereof radially to the central longitudinal axis and the inside end of which is provided with flexible support projections which combine to constitute a floating support ring, this ensuring lateral motions of the housing of an adjustable length element in the vicinity of the upper end of the column. These support projections have the double function of resiliently guiding the adjustable length element and of simultaneously offering sufficient rigidity to loads. Since the upright tube, the radial web-like ribs and the support projections formed on the latter all constitute a single piece of plastic material, the problem of compensation of tolerances of the inside diameter of the upright tube does not pose itself.